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A New Twist to Avoid Knee Injuries on the Slopes

Broken leg bones and ankles used to be all too common among alpine (downhill) skiers. Improvements in the design of ski bindings and boot releases have helped. Alpine skiers have their heels locked in and make parallel turns. So even with the reduced lower leg injuries, they've had a rise in knee injuries. These ski-related knee problems involve the anterior cruciate ligament (ACL) inside the knee joint.

If skiing equipment can be further redesigned to protect the knees, then knee injuries can be prevented. The first step in this process is to study the ACL and how it gets injured in ski accidents. Researchers at a biomechanics lab in California tested the knees of 37 cadavers (human bodies preserved for study).

Force was applied to each knee in four different positions. A twisting motion (twisting in or out) was applied to each position. This was to mimic the way the ACL is injured during skiing. The results showed that the twisting motion may not be the only key to knee injuries.

Twisting is an important part of ACL tears in skiers, but a fully bent position of the knee is the most important factor. This is called hyperflexion. Adding a twisting motion to a hyperflexed knee puts the ACL at great risk for injury. Likewise, combining a fully straight knee with a twisting-in motion is also a problem.

Alpine skiing injuries have been reduced over the past 20 years. New research may help lower the number of knee injuries in the next 20 years. Giving skiers protective gear and instructions based on research is the goal.

References: Sharon L. Hame, MD, et al. Injury to the Anterior Cruciate Ligament During Alpine Skiing. In The American Journal of Sports Medicine. July/August 2002. Vol. 30. No. 4. Pp. 537-540.

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